Shattered observatory is super fun! Dish out big deeps while moving slightly to the left/right, that's my kind of fight, lol. Twilight oasis under T4 is super fun as well. I actually don't mind thaumanova reactor, you just need a good healer.
Siren's reef needs to be deleted from this game though. I hate it more than I hate aquatic ruins, and I hate aquatic ruins with a deathly passion. Mai trin is also not a favourite, it's basically the slayer of PUGs...